I have not long moved into a new house and I'm starting to fit an alarm system.I have noticed the main panel has got a few relay outputs, including one for the alarm condition.I was hoping to be able to use an arduino with a GSM shield to send me and my girlfriend a text message if the alarm condition has activated.

This doesn't sound too hard... Wire up the relay contacts in the same way you would wire up a normal switch (only the relay does the equivalent of pressing the button), read the state of the input it's connected to, then send a text if it is high.Personally, I'd be very careful when playing with a securiy system. Unless you're absolutely sure about what you're doing, the results could be very dodgy. On the other hand, if you are sure, you could end up with a very useful system indeed!

Just found a good tutorial that seems fairly straight forward http://tronixstuff.wordpress.com/2011/01/19/tutorial-arduino-and-gsm-cellular-part-one/

Its using the sparkfun module I think, which is a bit pricey.

Just been checking ebay and they have modules from china for a fraction of the price like this one http://www.ebay.co.uk/itm/Arduino-Wireless-GSM-SIEMENS-TC35-SMS-Module-UART-232-/320771809651?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4aaf7d6173#ht_6452wt_1163 . Trouble is I don't think the documentation will be up to scratch and being new to this kind of thing I'm not sure I could cope with it lol, or would it be similar in useage to the sparkfun module?

I'm fitting the whole alarm system so I'm pretty much switched on with how it will work, I don't think I can cause any mischeif buy doing this project. There are PTS (push to set) terminals though which I might have a play with further down the line

page 120 of http://www.yourportablelab.com/downloads/schematics/AT_Command_Reference.pdf covers the details that should allow you to send text messages with the ebay shield, although it seems much more complex than the sparkfun shield. Out of the two, I'd pay the extra for the sparkfun shield, then you would know it will work, although it does cost more. Another option to consider would be to buy an ethernet shield. With the right code, you can make it send emails. I read somewhere about services that take an email you send them then send that as a text to a phone. If you can find such a service, that would provide another option.

There are PTS (push to set) terminals though which I might have a play with further down the line

That won't take long, generally only one function for those (or 2 on some panels). Push to terminate the exit timer with a possibility of being able to use the button as a doorbell in the unset state. If you have the front door contact set as exit terminate then you don't need the PTS button so it just becomes a doorbell. Might as well just fit a doorbell!

As for the GSM\SMS alarm shield, interesting idea, bearing in mind you're looking well over £100 for a manufactured alternative it's probably worth doing.

I guess you are right Onions, the sparkfun module does look a lot more user friendly, especially for a semi-noob like myself That's a good point about the Ethernet idea, I hadn't even considered that because I have not even got around to getting a phone line installed yet but that is certainly an option that I'm going to consider.

@Lurch, I know what you mean about the doorbell, I had an alarm on my old place and I fitted a door bell switch for a quick set when I went out the main door. I was thinking of something slightly different, though it might not work how I first thought. I also have one of these RFID proximity readers to fit http://www.tlc-direct.co.uk/Technical/DataSheets/Ade/TSSS01_Install.pdf they mention configuring the PTS input on the panel to accept a key switch input so I guess that would set the system? I wonder what protocol the 'comms' uses? Way out of my comprehension probably but it would be great to hack it to interface with an arduino lol.

That's what I thought, the factory units for telecomms are quite plus I would like the sense of achievement of doing things myself

I was thinking of something slightly different, though it might not work how I first thought. I also have one of these RFID proximity readers to fit http://www.tlc-direct.co.uk/Technical/DataSheets/Ade/TSSS01_Install.pdf they mention configuring the PTS input on the panel to accept a key switch input so I guess that would set the system? I wonder what protocol the 'comms' uses? Way out of my comprehension probably but it would be great to hack it to interface with an arduino lol.

Yeah, very closed protocols for a reason there! As for the PTS connection to the Simple Set, as per instructions just an alternative way of doing it. Basically on most panels you can program a zone as keyswitch which just arms\disarms the system as the zone opens and closes. All the Simple Set does is opens and closes this zone. The comms line is just for the zone feedback and programming. You could use any RFID reader or anything connected to an Arduino to set and unset the system using the same principle.

I'm pretty confused with the Simple Set reader to be honest. I have a Accenta G4 panel, but the instructions don't show the wiring to that panel only the G3, which I assume is an older system. I asked someone and they said don't use PTS for it because it communicates down the comms line - the same as the remote keypad. What do you think seems as you seem conversant with alarm systems?

Looking closer at the instructions the G3 uses the comms lines for set\unset and doesn't have the additional connection the the keyswitch zone\PTS circuit as the older panels do\did which I think is what the 'PTS uses the comms line" means. The ADE Simple Set will only work with the ADE panel (properly) but any RFID reader\proximity reader or any other set\unset device that can open\close a relay can set and unset the G4.

This is one reason I stopped using the ADE kit and became a proper alarm installer. On proper panels you can split the system into groups or areas and have seperate keyswitch inputs for the different groups so for example group A = whole house and group B = downstairs only. You could then set and unset group B by SMS at night. You could expand on this and have different commands for checking\setting\unsetting groups for upstairs\downstairs, day\night, outbuildings etc... You can also have more programmable outputs for more useful feedback to external devices on proper alarms so your Arduino could monitor the status and set\unset several groups or more.

They sound a lot more useful! How much more are the 'proper' panels? I guess I'm stuck with my panel for now, but running the sensor cables is the hard bit so I could always upgrade the panel in future

I'm assuming you're a relative novice in the intruder alarm panel arena so probably your best bet would be something like the Texecom Premier. Easily available, complete documentation and plenty of help via a couple of security forums. Can be expanded as required and you will be able to use your existing cabling and detection from your G4.